[2,2]-paracyclophane and its derivatives of the following general formula (III) ##STR2##
wherein X means a substituent selected from a group consists of hydrogen, chlorine, bromine, fluorine and alkyl; PA1 wherein n means the degree of polymerization,
form a poly-para-xylylene film (including a nucleus-substituted poly-para-xylylene film; and forth) on a substrate by chemical vapor deposition through the following reactions. In the following formula, n means the degree of polymerization: ##STR3##
According to this coating method, it is possible to form coating films over substances of all shapes such that the films are true to the shapes, and thus formed polymeric thin films are excellent in gas barrier and electric characteristics and are widely used as materials of electronic parts or for coating of space apparatus.
However, a poly-para-xylylene film prepared from the compound of the above formula (III) has a limit in use in spite of its excellent characteristics. It is that said poly-para-xylylene film, though having a wide application range in vacuum and nitrogen, has a limited application temperature in atmosphere because the structure --CH.sub.2 --CH.sub.2 -- binding benzene nuclei in its polymeric structure is liable to be oxidized. For example, this poly-para-xylylene film loses flexibility and strength as a film at 200.degree. C. within about 30 minutes in atmosphere to get ragged only by slight rubbing though at variance to some degree with the presence or absence of a substituent of the benzene nuclei and the kind of substituent. As a countermeasure against this, it has been proposed to add an antioxidant into the film (See U.S. Pat. Nos. 4,176,209 5,267,390 and 5,270,082), which however brings no essential solution.
In order to broadly apply the poly-para-xylylene film in various fields, it is required to increase the thermostability of the film in the presence of oxygen.
It is known that a poly-para-xylylene of the following formula in which hydrogens of its methylene group are all substituted by fluorine ##STR4##
has an outstanding thermostability. As to a process for manufacturing octafluoro-[2,2]-paracyclophane which is a starting material for the manufacture of this polymer, there are some patents and a patent application (see U.S. Pat. Nos. 3,268,599 3,274,267 and 3,297,591 and Japanese Patent Laid-open No. 255,149/1993).
However, mass production of these compounds is difficult and the films prepared therefrom have problems in adhering to substrates and the like. The objective of the present invention is to provide a new compound of the formula (I), dichloro-tetrafluoro-[2,2]-paracyclophane, which can be readily produced and is useful to form heat-resistant poly-paraxylylene film. Another objective of the present invention is to provide a highly thermostable poly-para-xylylene film prepared from said new compound.